Update LightTable integration instructions
Update LightTable integration instructions

Changed the installation instructions for LightTable to provide greater detail to new users.
nukisman/elm-format-short,avh4/elm-format,nukisman/elm-format-short,nukisman/elm-format-short,nukisman/elm-format-short,avh4/elm-format,nukisman/elm-format-short,avh4/elm-format,avh4/elm-format